For the first time, scientists have published details of the largest deep ocean eruption to ever happen in world history, which occurred in 2012 along the Kermadec Arc.
Five years ago, satellites detected a gigantic pumice raft at the northern coast of New Zealand. It later grew larger in size to about 400 square kilometers or the size of Philadelphia, signaling an unusually large submarine eruption.
Such unusual sighting was produced by the Havre Volcano, an underwater volcano lying 1,600 meters below the Pacific Ocean with a caldera measuring 4.5 kilometers across. The eruption consisted of lava expelled from 14 vent sites located between 900 and 1220 meters under the surface of the sea.
Details of the event were not revealed immediately, however. Scientists had to gather information through complicated methods such as mapping 50 square kilometers of seafloor with the AUV Sentry. The underwater vehicle was used for a total of 11 dives.
Moreover, a report states that another 12 dives totaling to 250 hours were conducted using the ROV Jason. These dives were aimed toward collecting samples of erupted material and capturing detailed images of the underwater volcano's crater.
Submarine Eruptions Produce Lava Flows And Domes
In a study published last Jan. 3, an international team of scientists from University of Tasmania, University of California Berkeley, the University of Otago in New Zealand, and the Woods Hole Oceanographic Institution report that the eruption history of the Havre Volcano is more complex than previously thought.
Underwater eruptions were believed to produce mainly pumice but the 2012 event was found to have also expelled ash, with 75 percent of the erupted material floating to the surface and drifting away due to winds and currents. New formations were also created by the eruption, such as lava flows and domes.
"When we looked at the detailed maps from the AUV, we saw all these bumps on the seafloor and I thought the vehicle's sonar was acting up. It turned out that each bump was a giant block of pumice, some of them the size of a van. I had never seen anything like it on the seafloor," says Adam Soule, associate scientist at WHOI.
Samples collected by ROV Jason showed the diversity of materials produced by the eruption. It brought dense evidence of lava, ash, and pumice, including a piece measuring 5 feet in diameter. Such sample is the first of its to ever be collected from the surface of the ocean and is currently displayed at Tokyo's National Museum of Science and Nature.
The team first studied the Havre Volcano in 2002 and then in 2012 right after its eruption. They returned in 2015 to retrieve samples exhibiting how volcanic materials can change over time.
What Are Deep Ocean Volcanoes?
A deep ocean or submarine volcano is a formation found thousands of feet underwater and is, therefore, hard to find. Because of this, documenting their activity have always presented a challenge to scientists.
Aside from the eruption of Havre Volcano, a separate team was able to capture the deepest submarine eruption. It occurred when the West Mata Volcano erupted nearly 4,000 feet below the surface.
Located between Samoa, Fiji and Tonga, the volcano produced a variety of molten rocks when it erupted in May 2009, including Boninite lavas that are thought to be among the hottest on Earth.